When merging maps or other atlas's into an atlas on a cartography table it allows you to merge maps that already exist in that atlas again giving the atlas a redundant map.

For example:

• Create a map (lets say it is an id of 1)
• Create a copy of that map
• Create an atlas out of one of those maps
• Merge your extra map into that atlas
• The Atlas now has two maps of ID 1

The worst case of this is when merging or duplicating atlases, so for example say I made a copy of an atlas for safe keeping, went out exploring expanding the atlas then when I go to home to update the old atlas any overlap any maps that overlap between the two atlases have will now have two copies, do this multiple times and that two becomes 4, then 8... you get the idea.

In an ideal world any overlaps (i.e. maps that occupy the same area) would get dropped in favor of the newest map but at a minimum maps with the same id should not get duplicated when merging atlases or merging maps into atlases to avoid the feedback loop described above.

Mod Version: 1.21-6.3.6-neoforge
Game version: 1.21.1
Neoforge Version: 21.1.211